At its homepage, nih.gov is protected by Cloudflare. Typical approach to reach it reliably: Matched TLS/JA3-JA4 + realistic headers on open paths. Difficulty is per-URL, so deep pages — profiles, listings, search — are usually harder.
Free WAF/CDN paths weigh IP reputation and header validity; a fingerprint-matched HTTP client usually reaches them. A managed challenge (“Just a moment”) needs a JS-running browser to earn cf_clearance.
Typical access
Headless browser that runs JavaScript
Why it didn’t pass cleanly
Bot challenge
A JS / bot challenge interstitial was served.
Detected vendors
Evidence
Detection confidence: high
Homepage-level, datacenter-IP snapshot, June 12, 2026.
This is a passive, homepage-level snapshot and can be inaccurate or out of date — anti-bot vendors update their models continuously, deep pages are usually more protected than the homepage, and a datacenter IP sees more challenges than a residential one. Treat it as a directional signal, not a guarantee.
The homepage is the open front door. On a government site the valuable pages behave differently — here's the plan to characterise nih.gov before you build.
Article / entry
usually openReference content is usually open.
Search
rate-limitedOpen but rate-limited at volume.
Find a real deep URL cheaply from the site’s robots.txt and sitemap.xml, then run each through the anti-bot checker. This is an advisory based on the category and nih.gov’s homepage result — detect the wall, never try to pass a login.